Measuring Brain Activity and Artificial Brain Modification

Electroencephalography (EEG)

used to record electrical activity of the brain.

S = good temporal resolution (discriminate very brief events in time), relatively cheap, portable and safe and well tolerated by participants

W = poor spatial resolution (difficult to determine precisely from which area signal has come from) and only detects activity on surface of cortex

Electrophysiology (Single Neurons)

from work of Hodgkin and Huxley - study of the electrical properties of neurons = insights into their activity and signaling mechanisms.

S = Records directly from individual neurons.

W = high risks of infections as invasive technique and only possible to record from a few neurons at a time (only individual or small network)

Magnetic Resonance Imaging (MRI)

Exploits the magnetic properties of brain tissue to generate detailed images. Magnetic field passes thru head causing hydrogen atoms to align with magnetic field and then generates images based on radiofrequency signals emitted as they return to their original alignment. Different brain areas have different amounts of water =emit different signals

Diffusion Tensor Imaging (DTI)

Detects large axon tracts using MRI equipment.

fMRI (Functional MRI)

Blood-oxygen-level-dependent signal, reflects change in oxygen levels in the blood.

• deoxygenated blood distorts surrounding magnetic field = blood vessels more visible

• as brain region uses energy = increase in blood flow to region provides real-time (slight delay of few secs) imaging of brain activity based on blood flow changes.

Strengths and Weaknesses of MRI

S = Very high spatial resolution (identify exactly where), can identify specific functional and structural properties.

W = very expensive, very large equipment that requires specialist facility, some safety risks due to large magnet and requires specialist staff

Positron Emission Tomography (PET)

Uses radioactive tracers to visualize glucose metabolism or neurotransmitter/receptor function. Also can use radioactive tracers to bind selectively to proteins of interest = diagnostic tool for Alzheimer’s

S = detects different chemicals associated with metabolism or specific neurotransmitter levels or receptors

W = expensive, specialist facilities and staff, relatively low spatial resolution, some risks due to radioactive tracers

Enhancement (Brain Modification)

Improvement of healthy function beyond normal.

Ablation Studies

Deliberate lesions to allow a relatively high degree of precision in studying brain function.

Frontal Leucotomy

Surgical ablation procedure involving removal/separation of the frontal lobes = linked personality to frontal lobes - no longer done. 2 methods

• a leucotome inserted into 1 of several holes drilled in skull>wire was then extruded from tip and leucotome rotated to remove a core of tissue

• cutting implement inserted above eyelid and pushed through base of skull>rocked side to side to slice through frontal lobes

Initial impression of improvements that led to widespread use but shown to be ineffective as led to profound personality consequences including apathy, emotional unresponsiveness, inability to plan

Electrical Brain Stimulation

Electrical stimulation to reveal precise localization of cortical function.

Electroconvulsive Therapy (ECT)

Electrical stimulation strong enough to cause a seizure, used to treat severe depression.

• most common method is transcranial direct current stimulation (tDCS)

Transcranial magnetic stimulation (TMS)

Non-invasive- coil carrying an electrical current generates brief focal magnetic pulse = activates small region of cortex = acts as visual lesion that temp disrupts the tissue

Pharmacology/Drugs

Can impact every stage of neurotransmitter function from synthesis to receptor binding